The invention relates to shaped solid sources of an active bleach that can be used in bleaching or cleaning processes. Active bleach is a common component of many washing or sanitizing processes including washing of kitchenware, tableware, flatware, cookware, etc., laundry, health care appliances, food manufacturing equipment, pharmaceutical manufacturing equipment, etc.
A variety of active bleaching compositions are known including active halogen bleaches. Active halogen compositions have been used for many years in a variety of cleaning or sanitizing methods. Such halogen sources can come in the form of gases (gaseous Cl2, Br2, etc.), liquids (aqueous sodium hypochlorite), or solids, calcium hypochlorite, chlorinated sodium tripolyphosphate, chlorinated isocyanuric acid and others. Solids can be dissolved in water to create a bleach concentrate. Such materials can be applied to processing by metering a gas or liquid form of the halogen source into the wash site into an aqueous stream directed to the wash site. Solid halogen sources can be used in a variety of washing processes by adding solids directly to the washing liquor or by metering an aqueous solution of the chlorine source into the wash locus.
Solid sources of halogen bleaches have been used in both aqueous solutions, particulate powders or in solid tablet or brick form. The solid tablet or brick form of the solid active bleach source can pose a problem in control of dispensing. Tablets or bricks of the material are introduced into aqueous dispensers. The dispensers can be calibrated to provide various bleach concentrations, often to provide 1 to 10 grams of halogen per bleach cycle. Within the dispenser the tablet or tablets are fixed mechanically at a fixed distance from an aqueous spray. As the aqueous spray contacts the surface of the solid bleach material the water dissolves a portion of the bleach source creating a liquid concentrate solid which is directed to a wash/bleach cycle. However, water can be absorbed by the tablet and can soak through the entire tablet or brick. The water can pass through this brick and can pass further into adjacent tablets or bricks. The absorbed water can cause the tablet(s) or brick(s) to become cracked, split, crumbled or become xe2x80x9cslushyxe2x80x9d. Such water soaked tablets often become difficult to dispense with adequate control of bleach concentrate in the wash liquor. Parts of the tablet can randomly be released by a disintegrating tablet causing random dispensing of undesirable, harmful, substantially large concentrations of halogen into the washing site. In the instance that the slushy or cracked tablet releases a substantial proportion of its mass into the dispenser, the dispenser can release 100-300 grams or more of chlorine source into the washing locus. Such high concentrations of chlorine can cause metal corrosion to washer or dispenser, fabric damage, color change or other harmful results.
The encapsulation of active sources of halogen bleach with organic and inorganic coatings have been disclosed in Brubaker, U.S. Pat. No. 4,279,764; Brennen, U.S. Pat. No. 3,637,509; Idudson, U.S. Pat. No. 3,650,961; Alterman, U.S. Pat. Nos. 3,983,254 and 3,908,045. Olson, U.S. Pat. No. 4,681,914, teaches the use of encapsulated sources of active halogen in cast solid warewashing detergents. In Olson, the encapsulated halogen source is dispersed in a molten caustic material that solidifies to form a sodium hydroxide based warewashing material.
Accordingly, a substantial need exists in processes using aqueous sources of halogen to provide a solid halogen source that can dispense a uniform proportion of the solid mass of the halogen source without uncontrolled dispensing problems.
We have found that control over dispensing solid bleach tablets can be obtained by manufacturing a tablet from a source of oxidant halogen bleach including an encapsulated source of oxidant halogen bleach. Alternatively, the tablet or solid can comprise both an unencapsulated powder or granular bleach source and the encapsulated source. The resulting tablets comprise a continuous solid phase comprising an unencapsulated source of oxidant bleach with the encapsulated source of bleach dispersed in the continuous phase. When used together the unencapsulated bleach can be used at a concentration of 20-90 wt % of the tablet and the encapsulated source of chlorine can be used in the tablet at a concentration of about 10 to 80 wt % based on the tablet. We have found that the encapsulated chlorine source aids in tablet formation and substantially reduces the harmful effects of water spray on the solid material. The tablets of the invention can be placed in the dispenser wherein the tablets are contacted with a water spray that creates an aqueous bleach concentrate. The water spray dissolves controlled amounts of the tablet to introduce into the wash liquor a consistent well controlled concentration of a halogen such as chlorine.
For the purpose of this invention the term xe2x80x9cbrickxe2x80x9d, xe2x80x9ctabletxe2x80x9d or xe2x80x9cblockxe2x80x9d connotes a mass of material greater than about 1 gram having a size and shape adapted for introduction into a dispenser to be contacted with a dissolving/dispensing water spray. The water spray, dissolving a controlled portion of the tablet forms an aqueous bleach concentrate that can be directed to a use locus such as a washing machine. The term solid source of oxidant bleach or active halogen bleach relates to a powder, granular, or other pourable solid material that can release active bleach under washing conditions. Aqueous bleach concentrates made using the tablets of the invention can contain up to about 10,000 parts per million of active oxidant bleach per million parts of aqueous solution. Such concentrate can be directed into a wash liquor in a wash machine and can be used at a concentration of a preferred source of active chlorine in contact with a soiled article in amounts of about 5 to 500 parts of active chlorine per million parts of wash liquor. The tablets of the invention are preferably made by blending a powdered source of chlorine with an encapsulate source of chlorine in a particulate form. The blended powder is then preferably compressed into tablets using available technology.
In our experimentation leading to the invention a number of materials were used to bind powdered or granular sodium dichloroisocyanurate into useful tablets. Additives such as Carbowax, fatty acids, inorganic materials, etc. were used as binders in common compression molded tableting operations. Overall, we have found that inorganic materials aid in tableting but failed to reduce the tendency of the chlorine source to absorb water leading to crumbling and uneven dispensing. We have found that some organic materials form adequate tablets with useful dispensing properties but are unstable in the presence of the highly active chlorine source. At high temperatures the material can discolor or smolder at concentrations useful in tableting. Further, we have found other additive materials that form useful tablets but introduce substantial hydrophobicity into the tablets leading to a failure to dispense adequate proportions of oxidizing bleach. We have found that the encapsulated oxidizing bleach source provides a number of advantages. First, the encapsulated bleach source acts as a binder material permitting the formation of mechanically stable shaped solids of halogen releasing material. Further, the coating of the encapsulated oxidizing bleach provides control over the hydrophobicity of the tablet leading to the dispensing of controlled amounts of the active bleach. The encapsulated chlorine source, while acting as a binder and dispensing control agent, does not substantially dilute the concentration of chlorine in the tablet. Lastly, the presence of the encapsulated source provides a stable tablet which can dispense a controlled even proportion of the solid material into the aqueous concentrate which is then directed to a cleaning locus for cleaning action on a variety of articles. The bleach source can be used to clean dishware, tableware, kitchenware, laundry, sheets, towels, food production equipment, pharmaceutical production equipment and any other related surface that requires bleaching, Sanitizing or other action of oxidizing bleaches.